1. Field of the Invention
The present invention relates to improvements in silencers and, more specifically, to a silencer used for a compressor for compressing contaminated gas including impurities such as tar or dust.
2. Description of the Related Art
In compressors of middle size or more, a silencer is mounted in the middle of a gas discharge pipe in order to reduce noise of compressed gas to be discharged. Silencers fall into two types and, concretely, sound extension type and sound absorption type, which are differentiated in sound reducing performance as described below. A sound extension type silencer is unfavorable in the sound reducing performance regarding to noise out of a sound reducing frequency range because its reducing frequency range is determined, while a sound absorption type silencer is excellent in the sound absorbing performance regarding to a wide range of frequencies. However, the sound extension type silencer is generally used more, for example, in an oil-cooled screw compressor for discharging oil-containing gas in spite of its inferior sound reducing performance to the sound absorption type silencer, since the sound absorbing performance of the sound absorption type silencer is significantly reduced when liquid is absorbed into a sound absorbing material. However, a sound absorption type silencer adapted to be usable in such an oil-cooled screw compressor for discharging oil-containing gas is also known.
For example, a silencer shown in FIGS. 12 and 13 is disclosed in Japanese Patent No. 3275527. FIG. 12 is a sectional view of a sound absorption type silencer according to the related art, and FIG. 13 is a perspective view of the same.
As shown in FIGS. 12 and 13, a muffler 50 according to the related art comprises a cylindrical case 45 having bottoms 44 with openings 43 at both ends, and a sound muffling material 51 which consists of a soft porous synthetic resin and is provided on the inside of the case where an air flow passage 46 communicating with the openings 43 is arranged in the center. A plurality of the sound muffling materials 51 are laminated in the axial direction, and skewered with axial bars 53 through holes 52 on the outside of the air passage 46 so as to prevent the deformation of the air flow passage 46 caused by the dynamic pressure of the gas treated. The bars 53 are fixed to a retaining plate 54 having an outer shape contacting with an inner wall of the case 45 while having the air flow passage 46 in the center part.
In case of a COG (coke oven gas) compressor, which compresses coke oven gas containing tar or dust, the coke oven gas containing tar and dust is passed through an inner part of the sound absorption type silencer. The tar or dust (hereinafter referred to as impurities) contained in the coke oven gas is adhered to the sound absorbing material or the inner part to deteriorate a sound absorbing effect of the sound absorption type silencer. As a matter of course, in case of the sound extension type silencer, the impurities are also accumulated in the inner part to deteriorate the sound absorbing effect.
Accordingly, in order to continue a desired sound absorbing effect, either type of silencers needs periodic cleaning of the inner part to remove the deposits.
However, the silencer according to the conventional example has an integrated structure, which disables cleaning from the outside, as is understood well from the above description for its structure. Therefore, if cleaning is unavoidably required, the silencer is cut off and restored by welding after cleaning to reuse, or generally replaced by a new silencer, and thus has a problem such as an extremely troublesome work and increasing cost in maintenance of the silencer.